SImulation of an electrostatically actuated beam

Hi,

I am new to COMSOL and presently trying to simulate the pull-in instability of electrostatically actuated micro beams in COMSOL MEMS module. I need further insights into the following topics pertaining to this problem:

1) Has anyone benchmarked some typical beam problem so that one can have some idea about what is the optimum number of elements; say along beam-length, width, thickness? I have followed the tutorial problem in COMSOL and the results do match with the literature, but just checking if someone has already tried this out.

2) How do we decide the optimum dimensions of the surrounding box (air chamber) in which the electrostatic problem is solved. I have observed that making it too small changes the results substantially and making it big increases the number of elements in the electrostatic domain, and hence the computational effort.

3) How do we ensure that the charge distribution over the surface of the beam is accurately captured? I feel that turning on the weak constraints would help, however, just curious if somebody is having a better understanding and/or previous insights from their own numerical experiments.

Thanks in anticipation for your time and valuable inputs.


Dekar